CHARACTERIZATION OF BACTEROIDES-FORSYTHUS ISOLATES

Fifteen Bacteroides forsythus strains freshly isolated from patients w ith periodontitis were used together with three collection strains and one type strain for characterization of growth on various media; dete rmination of enzymatic profiles, antibiotic susceptibility profiles, 1 6S rRNA ribotypes, sodium dodecyl sulfate-polyacrylamide gel electroph oresis (SDS-PAGE) outer membrane protein profiles, and pathogenicity; and gas chromatography analysis by using a wound chamber model in rabb its, All strains were stimulated by N-acetylmuramic acid, while one st rain needed a further supplement such as yeast extract for optimal gro wth, All strains showed trypsin-like activity, While 10 different ribo types were found, the SDS-PAGE profiles revealed similar patterns for all strains, All strains were sensitive to penicillin G (MICs, <0.5 mu g/ml), ampicillin (MICs, <1.0 mu g/ml), amoxicillin (MICs, <0.38 mu g /ml), metronidazole (MICs, <0.005 mu g/ml), tetracycline (MICs, <0.19 mu g/ml), doxycycline (MICs, 0.05 mu g/ml), erythromycin (MICs, <0.4 m u g/ml), and clindamycin (MICs, <0.016 mu g/ml), while they were less sensitive to ciprofloxacin (MICs, <4 mu g/ml). B. forsythus did not ca use abscess formation by monoinoculation. B. forsythus coinoculated wi th Fusobacterium nucleatum ATCC 10953 caused abscess formation in 75% of rabbits, while it caused abscess formation in 100% of rabbits when it was coinoculated with Porphyromonas gingivalis FDC 381. In the case of the latter combination, four of six rabbits died of sepsis after 6 to 7 days, and P. gingivalis and B. forsythus were recovered from the heart blood at a proportion of 10:1, B. forsythus strains were highly virulent and invasive in combination with P. gingivalis.